Summary Vascular smooth muscle cells (VSMC) play a critical role in the etiology and progression of many vascular diseases including atherosclerosis and restenosis. Reduction of inflammatory gene expression in VSMC is a rational approach to limit the severity of these diseases. Our laboratory has found that one anti-inflammatory interleukin, IL-19, can decrease vascular inflammation by reduction in mRNA stability of inflammatory transcripts by reduction of activity of HuR, an mRNA stability protein. HuR translocates from the nucleus to the cytoplasm where it recognizes elements present almost exclusively in the 3'UTR of pro-inflammatory genes. Proteins and pathways which limit HuR translocation are understudied, but may reduce inflammatory mRNA stability. Using MASS SPEC to identify HuR-interacting proteins under different inflammatory conditions, we identified one protein, Fragile X-related protein (FXR1), which interacts with HuR in inflammatory, but not basal conditions. FXR1 is a putative mRNA binding protein, but its interaction with HuR is novel. Interestingly, FXR1 mRNA expression is enhanced in muscle cells, and its promoter contains multiple cholesterol-response elements. Nothing has been reported on expression of FXR1 in VSMC or function for FXR1 in vascular disease. Nothing at all has been reported on FXR1 interaction with HuR in any other cell. Our preliminary data shows that FXR1 expression is increased in injured arteries and TNF? and oxLDL stimulated human VSMC, as well as by IL-19. However, siRNA knock down of FXR1 in VSMC increases abundance of inflammatory proteins; therefore, our overall hypothesis is that FXR1 expression and HuR interaction is an inflammation responsive, counter-regulatory mechanism to reduce abundance of pro-inflammatory proteins. The overall goal of this application is twofold: 1- to characterize the molecular mechanisms of FXR1 function in regulation of HuR activity and mRNA stability of pro-inflammatory transcripts in VSMC, and; 2- determine if modulation of FXR1 activity or expression can reduce severity of vascular restenosis. Very little is understood concerning negative regulation of inflammatory mRNA stability, and nothing at all is known about FXR1 expression and function in VSMC and vascular disease. The completion of these aims will clarify molecular mechanisms of anti-inflammatory compounds and uncover a novel role for FXR1 in vascular disease.